For what it's worth, his Encyclopedia Dramatica entry [1] is in the series "Leaders of Anonymous", along with Sabu, Ryan Clearly, etc. It's pretty well known that he was heavily involved, but like most things on IRC and 4chan, the text is ephemeral and/or private, so there's no good records other than miscellaneous pastebins.
On the other hand, I found a decent comment [2] from someone who seems to know what they're talking about that suggests he was just an eager journalist that got pulled too far into this whole thing.
For a quick overview of much of Anonymous's history, I recommend the documentary We are Legion [3]. It features an interview with Barrett Brown, and I think has a much better handle on the whole situation than most MSM reporting does.
Um, I'm not sure why you felt the need to point this out because anyone who visits the site knows that. I can't fathom how you think someone might not comprehend that.
Don't take everything so literally. Just because the site is full of unabashed trolling, doesn't mean you can't read between the lines and see that my point still stands.
-- Edit --
The reason you don't see any recent MSM articles referring to Barrett Brown as a "leader" of Anonymous is because they don't know what they're talking about. If you want to know the extent of his involvement you have to go to sources published by people who at least have paid attention to this whole situation for reasons besides pageviews. You need to hear from people who have been following the situation for more than just the past month.
But as expected, the closer you get to Anonymous, the more "uncredible" the sources look. Sure, ED and 4chan are rife with trolling -- everyone familiar with the subject beyond today's news article should know that.
However, that doesn't mean these sources don't have merit. They're written by people who know more about the issue than the MSM. They're written by people who (1) know what they are talking about but are (2) trying to troll people who don't know what they're talking about. But you don't have to tease out much misinformation to see that Brown has a long history with Anonymous, and is more than just a "journalist".
On the other hand, I found a decent comment [2] from someone who seems to know what they're talking about that suggests he was just an eager journalist that got pulled too far into this whole thing.
For a quick overview of much of Anonymous's history, I recommend the documentary We are Legion [3]. It features an interview with Barrett Brown, and I think has a much better handle on the whole situation than most MSM reporting does.
[1] https://encyclopediadramatica.se/Barrett_Brown
[2] http://www.reddit.com/r/anonymous/comments/zt41f/barrett_bro...
[2] http://wearelegionthedocumentary.com/